thumb|upright|Manhigh II balloon gondola displayed at the National Museum of the U.S. Air Force, Wright-Patterson AFB, Ohio
right|thumb|As displayed in 2018
Project Manhigh was a pre-Space Age military project that took men in balloons to the middle layers of the stratosphere, funded as an aero-medical research program, though seen by its designers as a stepping stone to space. It was conducted by the United States Air Force between 1955 and 1958.
History
The project started in December 1955 to study the effects of cosmic rays on humans. Three balloon flights to the stratosphere were made during the program:
- Manhigh I to , by Captain Joseph W. Kittinger on June 2, 1957. The balloon was launched from South St. Paul Airport and the flight was cut short due to one of the capsule's valves being installed backwards which vented the oxygen supply outside, but not before reaching a record altitude of 96,784 feet. With the pilot and the scientific payload, the Manhigh II gondola had a total mass of . At maximum altitude, the balloon expanded to a diameter of with a volume of over .
- Manhigh III to , by Lieutenant Clifton M. McClure on October 8, 1958
Candidates for the Manhigh project were put through a series of physical and psychological tests that became the standard for qualifying astronauts for the Project Mercury, America's first crewed orbital space program.